sql - 合并两列然后分组

Question

我有以下表格和数据，我想将 loc1 和 loc2 合并在一列中，并从 loc 列中删除重复值，然后根据 group_no 列对其进行分组。

drop table test;
create table test (loc1 number(9), loc2 number(9), group_no number(9));
insert into test values(2,3,1);
insert into test values(2,9,1);
insert into test values(4,3,1);
insert into test values(6,8,2);
insert into test values(11,7,2);
insert into test values(20,15,2);
insert into test values(15,14,2);
insert into test values(21,31,3);
insert into test values(31,32,3);

预期结果是：

loc   group_no
2        1
3        1
9        1
4        1
6        2
8        2 
11       2
20      2 
15       2
21       3
31       3
32       3

问候

Answer 1

根据您的预期结果，您想要分组loc而不是group_no.

select t.loc, max(t.group_no)
(
    select loc1 as loc, group_no from test

    union

    select loc2 as loc, group_no from test
) t
group by t.loc
order by 2,1